| 摘要 |
PURPOSE:To obtain an efficient analog/digital communication equipment by inserting a constant voltage element in series with a transmission line so as to activate a switching element connected in parallel in response to a digital signal. CONSTITUTION:A current I by a power supply B inserted in series with a 2-wire transmission line is controlled in response to a data such as measuring value by a transmitter 2 connected to the other end of the transmission line 1, the current value is transmitted as an analog signal changed within a prescribed range and received by a receiver 3. A Zener diode ZD is inserted to the line 1 as the constant voltage element in a direction producing a Zener voltage VZ and a switching element Q1 in the communication equipment 4 connected in parallel therewith is turned on/off in response to a digital signal to be transmitted to the transmitter 2. When the diode ZD is inserted or short-circuited in response to the on/off of the Q1, the voltage VZ is generated or lost, a line voltage VL of the transmission line 1 is changed pulsively and the transmitter 2 receives the digital signal. |
